On Wed, Nov 30, 2016 at 2:54 PM, Bin Cheng <bin.ch...@arm.com> wrote: > Hi, > Loop header PHI defining IV(biv) may not be identified as biv because its > increment statement is in (irreducible) inner loop. Function > find_deriving_biv_for_expr doesn't take this into consideration and runs into > infinite recursion. The patch fixes this issue by skipping such loop header > PHI. Bootstrap and test on x86_64 and AArch64, is it OK?
Ok. Richard. > BTW, we don't mark such IV as biv because of below code: > > /* If the increment is in the subloop, ignore it. */ > incr_bb = gimple_bb (SSA_NAME_DEF_STMT (var)); > if (incr_bb->loop_father != data->current_loop > || (incr_bb->flags & BB_IRREDUCIBLE_LOOP)) > continue; > > I thought twice and this check may be too strict. Given valid incr_iv > returned by simple_iv, we know it behaves just like usual increment IVs. In > other words, though the increment statement is executed multiple times in > inner loop, it computes the same result for every iteration. Anyway this is > stage1 work. > > Thanks, > bin > > 2016-11-30 Bin Cheng <bin.ch...@arm.com> > > PR tree-optimization/78574 > * tree-ssa-loop-ivopts.c (find_deriving_biv_for_expr): Skip loop > header PHI that doesn't define biv. > > gcc/testsuite/ChangeLog > 2016-11-30 Bin Cheng <bin.ch...@arm.com> > > PR tree-optimization/78574 > * gcc.c-torture/compile/pr78574.c: New test.
